Statically allocating buffers in Wire library (issue #351).

Author: damellis

libraries/Wire/Wire.cpp

@@ -28,12 +28,12 @@ extern "C" {
 
 // Initialize Class Variables //////////////////////////////////////////////////
 
-uint8_t* TwoWire::rxBuffer = 0;
+uint8_t TwoWire::rxBuffer[BUFFER_LENGTH];
 uint8_t TwoWire::rxBufferIndex = 0;
 uint8_t TwoWire::rxBufferLength = 0;
 
 uint8_t TwoWire::txAddress = 0;
-uint8_t* TwoWire::txBuffer = 0;
+uint8_t TwoWire::txBuffer[BUFFER_LENGTH];
 uint8_t TwoWire::txBufferIndex = 0;
 uint8_t TwoWire::txBufferLength = 0;
 
@@ -51,13 +51,9 @@ TwoWire::TwoWire()
 
 void TwoWire::begin(void)
 {
-  // init buffer for reads
-  rxBuffer = (uint8_t*) calloc(BUFFER_LENGTH, sizeof(uint8_t));
   rxBufferIndex = 0;
   rxBufferLength = 0;
 
-  // init buffer for writes
-  txBuffer = (uint8_t*) calloc(BUFFER_LENGTH, sizeof(uint8_t));
   txBufferIndex = 0;
   txBufferLength = 0;
 

libraries/Wire/Wire.h

@@ -27,12 +27,12 @@
 class TwoWire
 {
   private:
-    static uint8_t* rxBuffer;
+    static uint8_t rxBuffer[];
     static uint8_t rxBufferIndex;
     static uint8_t rxBufferLength;
 
     static uint8_t txAddress;
-    static uint8_t* txBuffer;
+    static uint8_t txBuffer[];
     static uint8_t txBufferIndex;
     static uint8_t txBufferLength;
 

libraries/Wire/utility/twi.c

@@ -40,15 +40,15 @@ static uint8_t twi_slarw;
 static void (*twi_onSlaveTransmit)(void);
 static void (*twi_onSlaveReceive)(uint8_t*, int);
 
-static uint8_t* twi_masterBuffer;
+static uint8_t twi_masterBuffer[TWI_BUFFER_LENGTH];
 static volatile uint8_t twi_masterBufferIndex;
 static uint8_t twi_masterBufferLength;
 
-static uint8_t* twi_txBuffer;
+static uint8_t twi_txBuffer[TWI_BUFFER_LENGTH];
 static volatile uint8_t twi_txBufferIndex;
 static volatile uint8_t twi_txBufferLength;
 
-static uint8_t* twi_rxBuffer;
+static uint8_t twi_rxBuffer[TWI_BUFFER_LENGTH];
 static volatile uint8_t twi_rxBufferIndex;
 
 static volatile uint8_t twi_error;
@@ -88,11 +88,6 @@ void twi_init(void)
 
   // enable twi module, acks, and twi interrupt
   TWCR = _BV(TWEN) | _BV(TWIE) | _BV(TWEA);
-	
-  // allocate buffers
-  twi_masterBuffer = (uint8_t*) calloc(TWI_BUFFER_LENGTH, sizeof(uint8_t));
-  twi_txBuffer = (uint8_t*) calloc(TWI_BUFFER_LENGTH, sizeof(uint8_t));
-  twi_rxBuffer = (uint8_t*) calloc(TWI_BUFFER_LENGTH, sizeof(uint8_t));
 }
 
 /*